Extrusion welding of AlZnMg alloys encounters great technological difficulties in practice associated with high shaping forces and the low quality of longitudinal welds. Three different chemical ...compositions of 7021 aluminum alloy, differing in terms of Zn and Mg contents, were used in the first stage of the research. The laboratory device modelling the behavior of metal in welding chambers of the porthole die was applied to examine the ability of 7021 alloys to produce high-quality joints. The weldability tests were carried out for different welding temperatures—400, 450 and 500 °C—and for a fixed welding pressure of 300 MPa. The microstructural effects in pressure-welds were evaluated with the use of OM and SEM/EDS. The temperature–pressure parameters in the welding chambers were analyzed by using the FEM method for original porthole dies while extruding tubes with dimensions of Ø50 × 2 mm. Finally, the industrial extrusion trials were performed with examination of the structure and strength of the seam welds. It was found that it is possible to produce high-quality high-strength welds in tubes extruded from AlZnMg alloys in industrial conditions (the strength of welds in the range of 96–101% of the strength of the basic non-welded material) through properly matched alloy chemical composition of the alloy, construction of the porthole dies and temperature–speed conditions of deformation.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Within the present work the homogenization of DC-cast (direct chill-cast) extrusion billets of Al-Mg-Si-Cu alloy was investigated. The alloy is characterized by higher Cu content than currently ...applied in 6xxx series. The aim of the work was analysis of billets homogenization conditions enabling maximum dissolution of soluble phases during heating and soaking as well as their re-precipitation during cooling in form of particles capable for rapid dissolution during subsequent processes. The material was subjected to laboratory homogenization and the microstructural effects were assessed on the basis of DSC (differential scanning calorimetry) tests, SEM/EDS (scanning electron microscopy/energy-dispersive spectroscopy) investigations and XRD (X-ray diffraction) analyses. The proposed homogenization scheme with three soaking stages enabled full dissolution of Q-Al
Cu
Mg
Si
and θ-Al
Cu phases. The β-Mg
Si phase was not dissolved completely during soaking, but its amount was significantly reduced. Fast cooling from homogenization was needed to refine β-Mg
Si phase particles, but despite this in the microstructure coarse Q-Al
Cu
Mg
Si
phase particles were found. Thus, rapid billets heating may lead to incipient melting at the temperature of about 545 °C and the careful selection of billets preheating and extrusion conditions was found necessary.
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In the realm of modern architecture, the demand for materials that combine strength, durability, and aesthetic flexibility is ever-growing. Addressing this need, this paper presents a study on the ...innovative use of aluminum extrudates in construction. Focusing on the AA6005 alloy, which is known for its excellent balance of strength, corrosion resistance, and weldability, this research delves into the development of an extrusion process that yields thin-walled, lightweight, yet high-strength structural components. Using FEM simulations, a new extrudate of the AA6005A was developed. It is compatible with standard façade systems, with high-strength properties and a weight reduced by 20% compared to that of conventional extrudates made of the AA6063 alloy. Using CAD engineering and FEM simulations of aluminum extrusion process, an innovative die was designed for the extrusion process, ensuring uniform flow of metal from the bearing and minimizing the elastic deflection of the die. This resulted in an increase in the extrusion velocity of thin-walled extrudate from AA6005A by 24% compared to conventional profiles extruded from AA6063. As part of the research, a trial test was carried out in production conditions and the quality of the extrudates was tested by 3D optical scanning, mechanical and structural properties tests, and microstructure observation.
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This article is a diagnosis of the facts based on inner, empirical research. The aim of the Article is to present the situation of international students in WSG University during the lockdown related ...to the COVID-19 pandemic and the implemented measures and activities to counter its negative effects. The examples will relate to Poland and the university I represent. This article deals with the following issues: general situation of international students in Poland, brief overview of the university's activities, what tools and procedures to adapt to the new situation were prepared in advance, and what should be implemented in a crisis situation, the challenges of a sudden increase in the level and quantity of distance learning and recruitment challenges of international students. The summary will be a presentation of good practices introduced at the university in the context of COVID-19, which can be implemented in many European universities.
Diatoms (Bacillariophyta) are unicellular photosynthetic organisms commonly occurring in aquatic habitats on Earth. Their autecology makes them almost perfect indicators of environmental conditions ...and so have high potential for use in forensics. Both eurytopic and stenotopic species are important in site identification: eurytopic forms due to their abundance, and stenotopic forms due to their narrow range of tolerance to environmental conditions. Their presence can hence provide a clear insight into an ecosystem and its microhabitats. The diatoms are useful as significant indicator in diagnosing of drowning. However, to definitively link a corpse with the place where it was found and to indicate whether this was also the crime scene, it is essential that any comparative diatomaceous analyses are performed correctly. The following study presents selected cases in which a comparative diatomaceous analysis was performed. In all cases, the biological samples secured during the autopsy were compared with environmental samples collected from the site of the cadaver disclosure. Our findings show both the possibilities and limitations of using this method in forensics. These forensic investigations need close collaboration between coroners and diatomology experts. It is crucially important to reveal whether the place of corpse finding is the same as the place of drowning.
•Diatoms as a helpful tool in diagnosing drownings.•Diatom analysis as a crucial step for confirming or excluding the site of drowning.•The necessity to secure diatom samples from the site where the body was found.•Possibilities of using comparative analysis of diatoms in forensics.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Environmental analysis of soil, water, and plants plays a key role in the criminal investigation process, as it not only provides information about the course of the crime, but it can also elucidate ...the connection between the offender, the victim, and the environment. One particularly useful way of linking the victim and offender to a specific environment is by analyzing their clothing for the presence of diatoms. The present research was conducted upon field experiments. Firstly, it examines the variability of diatom and the quantitative analysis of diatom communities in designated places, each at an increasing distance from the aquatic ecosystem. Secondly, it analyses the differentiation of the structure of diatom communities in designated environments located close to each other. Thirdly, it examines the diatom colonization of selected substrates: cotton, chamois leather, and sponge. Finally, it confirms whether the diatoms which transfer to socks after contact with the selected environment reflect the structure of the diatom communities in that environment, even after the socks had been washed. Our findings indicate that diatom communities vary considerably, even between environments separated by short distances, and that objects placed in a particular environment are colonized by diatoms that reflect the environmental samples, irrespective of the substrate. In addition, after contact with a specific aquatic ecosystem, sock material retained diatom collections that reflected the environment samples, even though the time of exposure was very short and after the socks had been washed. This provides valuable information that can be used as forensic evidence.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Okrzemki z powodu powszechności, ale i specyficzności występowania w środowiskach wodnych oraz ogromnej trwałości skorupki będącej podstawą do ich rozróżnienia gatunkowego mogą być istotnym ...czynnikiem rozstrzygającym o diagnozowaniu utonięcia jako przyczyny śmierci. W niniejszej publikacji wykorzystano protokoły sądowo-lekarskich oględzin zwłok oraz protokoły badania na obecność okrzemek w płucu i nerce sporządzone w latach 2015–2017 w Zakładzie Medycyny Sądowej Warszawskiego Uniwersytetu Medycznego, który jest jedynym ośrodkiem w Polsce przeprowadzającym rutynowo test okrzemkowy. Wykazano, iż test ten może być głównym czynnikiem rozstrzygającym co do przyczyny zgonu w przypadku badania zwłok objętych zaawansowanymi późnymi przemianami pośmiertnymi lub w sytuacji, gdy płuca doznały rozległych uszkodzeń.
Introduction
During COVID‐19 pandemic, artificial neural network (ANN) systems have been providing aid for clinical decisions. However, to achieve optimal results, these models should link multiple ...clinical data points to simple models. This study aimed to model the in‐hospital mortality and mechanical ventilation risk using a two step approach combining clinical variables and ANN‐analyzed lung inflammation data.
Methods
A data set of 4317 COVID‐19 hospitalized patients, including 266 patients requiring mechanical ventilation, was analyzed. Demographic and clinical data (including the length of hospital stay and mortality) and chest computed tomography (CT) data were collected. Lung involvement was analyzed using a trained ANN. The combined data were then analyzed using unadjusted and multivariate Cox proportional hazards models.
Results
Overall in‐hospital mortality associated with ANN‐assigned percentage of the lung involvement (hazard ratio HR: 5.72, 95% confidence interval CI: 4.4–7.43, p < 0.001 for the patients with >50% of lung tissue affected by COVID‐19 pneumonia), age category (HR: 5.34, 95% CI: 3.32–8.59 for cases >80 years, p < 0.001), procalcitonin (HR: 2.1, 95% CI: 1.59–2.76, p < 0.001, C‐reactive protein level (CRP) (HR: 2.11, 95% CI: 1.25–3.56, p = 0.004), glomerular filtration rate (eGFR) (HR: 1.82, 95% CI: 1.37–2.42, p < 0.001) and troponin (HR: 2.14, 95% CI: 1.69–2.72, p < 0.001). Furthermore, the risk of mechanical ventilation is also associated with ANN‐based percentage of lung inflammation (HR: 13.2, 95% CI: 8.65–20.4, p < 0.001 for patients with >50% involvement), age, procalcitonin (HR: 1.91, 95% CI: 1.14–3.2, p = 0.14, eGFR (HR: 1.82, 95% CI: 1.2–2.74, p = 0.004) and clinical variables, including diabetes (HR: 2.5, 95% CI: 1.91–3.27, p < 0.001), cardiovascular and cerebrovascular disease (HR: 3.16, 95% CI: 2.38–4.2, p < 0.001) and chronic pulmonary disease (HR: 2.31, 95% CI: 1.44–3.7, p < 0.001).
Conclusions
ANN‐based lung tissue involvement is the strongest predictor of unfavorable outcomes in COVID‐19 and represents a valuable support tool for clinical decisions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Any object on the globe, in addition to the gravitational force, is affected by the force associated with the rotation of the Earth, i.e., the centrifugal force, which together define the force of ...gravity. Due to various factors, both external (the influence of other celestial bodies) and internal (the inhomogeneous internal structure of the Earth), the gravity depends on the location and time of observation. The study on gravity is made possible by using extremely sensitive measuring devices called gravimeters, which are a branch of physical geodesy called geodetic gravimetry. Geodetic gravimetry is widely used in geodesy to study the shape of the geoid and the realisation of gravimetric control networks or in geophysics to detect mineral deposits, underground watercourses or caves. However, in order to obtain reliable results, it is necessary not only to measure the gravity accurately, but also to reduce these measurements adequately. This is possible by determining, among other things, the vertical gravity gradients (VGG), which are used to reduce the measured gravity values to any reference level. In our research, we focused on analysing the change in the value of VGGs in the closed area of the Military University of Technology (MUT). We used 33 points of the existing vertical and horizontal networks of the MUT for measurements. We performed the observations using ZLS Burris model B-67 spring gravimeter at several heights in the range of 0.1 m to 1.3 m using a specially constructed tripod. We showed that the values of the vertical gradients vary over the selected area from ‒0.2534 mGal/m to ‒0.3917 mGal/m. The obtained results show consistency with the spatial distribution of changes of the topography of the terrain, the density of the Earth’s crust, and the type of geological formations present beneath the surface. In the study, we also showed the relevance of using the actual (measured) values of gradients to analyse geoid-to-quasigeoid separation. We have shown that taking the actual gradient values instead of their average (or modelled) values results in deviations in modelling the separation of both geodetic reference surfaces of up to 2 mm in the study area.Keywords: gravity, vertical gravity gradient, gravimetry, geoid-quasigeoid separation
4M method is a new application of Mössbauer spectroscopy to quantitative classification of ordinary chondrites. 4M derives from four words: meteorites, Mössbauer spectroscopy, multidimensional ...discriminant analysis, Mahalanobis distance. This method was published by us in 2019. In this paper we present application of 4M method to classification of four meteorites. Link to script with calculation needed for classification of ordinary chondrites was given.
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